Internal combustion engines, such as diesel engines, typically include an electromechanical fuel injector assembly. The fuel injector assembly is electrically coupled to an engine control module which selectively causes the fuel injector assembly to inject or otherwise spray fuel through a fuel inlet valve and into a cylinder of the engine.
Fuel, such as diesel fuel, is drawn or aspirated into a central chamber or cavity of the fuel injector assembly through a fuel port. A plunger is urged toward an injector tip of the fuel injector assembly thereby increasing fluid pressure within the fuel injector assembly. The fuel injector assembly further includes a fuel spill valve which is mechanically coupled to a solenoid. When the fuel spill valve is in an open position, fuel is permitted to exit the fuel injector assembly through the fuel port thereby reducing fluid pressure within the fuel injector assembly. However, when the engine control module generates an injection pulse, the solenoid is actuated thereby causing the fuel spill valve to be positioned in a closed position. When the fuel spill valve is positioned in the closed position, fuel is not permitted to exit the fuel injector assembly thereby causing fluid pressure within the fuel injector assembly to increase rapidly as the plunger is urged toward the injector tip.
Once the pressure within the fuel injector assembly reaches a predetermined magnitude, a spring loaded check valve located in the injector tip unseats thereby causing fuel to be injected or otherwise sprayed into the cylinder. Fuel continues to be injected into the cylinder until the engine control module deactuates the solenoid. More specifically, fuel is injected into the cylinder throughout the duration of the injection pulse generated by the engine control module.
Fuel injector assemblies as described above have a number of drawbacks associated therewith. For example, as with any mechanical apparatus, performance of the fuel injector assembly may decrease over its useful life due to anticipated, yet unpredictable, wear. In particular, a number of the components associated with the fuel injector assembly may mechanically wear throughout the useful life of the fuel injector assembly. For example, the rate at which the fuel spill valve opens and/or closes may change over time thereby altering the amount of time between the point in time at which the engine control module transmits the injection pulse and the point in time at which fuel is actually injected into the cylinder. Moreover, the spring bias of the spring loaded check valve located in the injector tip may diminish over time due to wear thereby altering the amount of fuel which is injected into the cylinder.
In addition, the rate at which performance of a given fuel injector assembly decreases over the useful life thereof may be different than the rate at which performance of another fuel injector assembly associated with the same engine decreases. Hence, performance may disadvantageously vary from cylinder-to-cylinder in a given engine.
What is needed therefore is an apparatus and method for controlling a fuel injector assembly of an internal combustion engine which overcomes one or more of the above-mentioned drawbacks.